[PATCH 1/3] bitmap: introduce bitmap_weighted_xor()

["Yury Norov (NVIDIA)" <yury.norov@gmail.com>]

The function helps to XOR bitmaps and calculate Hamming weight of
the result in one pass.

Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
---
 include/linux/bitmap.h | 14 ++++++++++++++
 lib/bitmap.c           |  7 +++++++
 2 files changed, 21 insertions(+)

diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 0f4789e1f7cb..7ecf56e0d3b5 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -169,6 +169,8 @@ void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
 		 const unsigned long *bitmap2, unsigned int nbits);
 unsigned int __bitmap_weighted_or(unsigned long *dst, const unsigned long *bitmap1,
 				  const unsigned long *bitmap2, unsigned int nbits);
+unsigned int __bitmap_weighted_xor(unsigned long *dst, const unsigned long *bitmap1,
+				  const unsigned long *bitmap2, unsigned int nbits);
 void __bitmap_xor(unsigned long *dst, const unsigned long *bitmap1,
 		  const unsigned long *bitmap2, unsigned int nbits);
 bool __bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
@@ -355,6 +357,18 @@ unsigned int bitmap_weighted_or(unsigned long *dst, const unsigned long *src1,
 	}
 }
 
+static __always_inline
+unsigned int bitmap_weighted_xor(unsigned long *dst, const unsigned long *src1,
+				const unsigned long *src2, unsigned int nbits)
+{
+	if (small_const_nbits(nbits)) {
+		*dst = *src1 ^ *src2;
+		return hweight_long(*dst & BITMAP_LAST_WORD_MASK(nbits));
+	} else {
+		return __bitmap_weighted_xor(dst, src1, src2, nbits);
+	}
+}
+
 static __always_inline
 void bitmap_xor(unsigned long *dst, const unsigned long *src1,
 		const unsigned long *src2, unsigned int nbits)
diff --git a/lib/bitmap.c b/lib/bitmap.c
index 698d15933c84..bed32b8cd23a 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -382,6 +382,13 @@ unsigned int __bitmap_weighted_or(unsigned long *dst, const unsigned long *bitma
 	return BITMAP_WEIGHT(({dst[idx] = bitmap1[idx] | bitmap2[idx]; dst[idx]; }), bits);
 }
 
+unsigned int __bitmap_weighted_xor(unsigned long *dst, const unsigned long *bitmap1,
+				  const unsigned long *bitmap2, unsigned int bits)
+{
+	return BITMAP_WEIGHT(({dst[idx] = bitmap1[idx] ^ bitmap2[idx]; dst[idx]; }), bits);
+}
+EXPORT_SYMBOL(__bitmap_weighted_xor);
+
 unsigned long __bitmap_weight_from(const unsigned long *bitmap,
 				   unsigned int start, unsigned int nbits)
 {
-- 
2.43.0